Flotation for Agricultural Implements

ABSTRACT

An agricultural implement has front flotation wheels with a significantly increased diameter, increasing flotation and improving rolling characteristics, especially in soft soil conditions. The implement has a frame supported on front and rear wheels. Front flotation wheels are pivotally mounted to the frame about vertical axes. A hitch tongue is pivotally attached to the frame about a vertical hitch pivot axis. A wheel control mechanism connects the front flotation wheels to the hitch tongue, and is configured such that when the hitch tongue is in a neutral position the front flotation wheels roll in the operating direction, and pivoting the hitch tongue causes the front flotation wheels to pivot in the same direction.

PRIORITY

This application claims priority to Canadian Application Ser. No. 2,772,865, filed Mar. 30, 2012, incorporated herein in its entirety byreference.

BACKGROUND

This disclosure relates to the field of agricultural implements and inparticular such implements with increased flotation and resistance tosinking into soft soil.

A common problem that farmers can experience at seeding time is theinability to seed their crops because excessive soil moisture makes thefields unable to support the seeding equipment, typically due toexcessive or untimely rainfall. Sometimes as well heavy snow coverproduces a lot of moisture which must either run off the fields, beabsorbed by the soil or evaporate. A late, cool spring can slow the soildrying process considerably. Unfortunately, for maximizing crop yieldsand crop quality and also minimizing the chances of crop damage orcomplete crop losses for spring seeded crops, it is necessary forfarmers to seed their crops within the finite window of time indicatedas acceptable by past experience.

Seeding too late, especially in northern agricultural areas, exposes thecrop to the risk of frost before the crop matures. This risk isrecognized in some crop insurance regimes where crops must be seededbefore a specified date in order to qualify for crop insurance. As farmsizes, crop input costs, land costs, and the like increase, the negativeconsequences for failing to seed a crop increase as well.

Agricultural air seeders are typically used to place seed and fertilizerin the soil to plant a crop. Such air seeders typically include a framemounted on wheels for movement along the ground, and furrow openersmounted to the frame and spaced evenly across the width of the frame sothat furrows and thus seed rows are evenly spaced across the field. Theframe includes a hitch extending forward from the front end thereof andthe drawbar of a towing tractor is attached to the front end of thehitch by a pin, such that the frame is pivotally attached to the drawbarabout a vertical pivot axis provided by the pin.

To provide even emergence of the crop plants, and to maximize yields, itis desirable to place the seeds at a consistent depth beneath the soilsurface. One common design to accomplish this is to provide front andrear wheels along corresponding front and rear edges of the frame, sothat the front and rear edges are then at a distance above the groundthat is substantially the same regardless of ups and downs in the fieldterrain and is thus kept level. The furrow openers are located betweenthe front and rear wheels.

In air seeders with furrow openers mounted directly to the drill frame,the furrow openers extend the same distance downward from the frame sothat the depth to which each furrow opener penetrates the soil issubstantially the same, and is controlled by moving the front and rearwheels up and down with respect to the frame.

In air seeders with independent ground following openers, each furrowopener is independently mounted on an arm with a ground following wheel,and a hydraulic cylinder exerts a downward bias force between the frameand the arm that pushes the furrow opener into the soil, and forces theground following wheel against the soil behind the furrow opener to packthe soil over the seed. The relative position of the furrow opener andground following wheel is adjusted to substantially control thepenetration depth. The hydraulic cylinders also raise the arms totransport and lower them for field work.

Such independent furrow openers have been found to perform better insoft, wet soil conditions than the frame mounted openers, as the groundfollowing wheel prevents the furrow opener from sinking further into thesoil if the frame wheels sink in the soft soil. Seeding depth is thusbetter controlled, and the downward bias force exerted on the arm can bereduced where the soil is very soft. The weight of the implement is alsopartially carried on the ground following wheels, thus somewhat reducingthe weight on the front and rear frame wheels, and reducing the tendencyfor the front and rear frame wheels to sink into soft soil.

The rear wheels are typically fixed to the frame such that therotational axes thereof are perpendicular to the operating traveldirection. Typically as well, the front wheels are caster wheels thatcan pivot freely about a vertical caster axis. The fixed rear wheelskeep the implement moving in a straight line following the tractor,while the castering front wheels allow the implement to turn since therolling orientation of the caster wheels changes to follow the frame asit moves in a lateral direction during the turn.

A “floating” type hitch is pivotally attached to the frame about a hitchpivot axis oriented horizontally and perpendicular to the operatingtravel direction. The front end of the hitch connects to the tractordrawbar, and the floating hitch pivots up and down with the tractordrawbar and the frame as the tractor and implement move across a fieldand as terrain varies. This same arrangement is used on agriculturalimplements such as cultivators and the like, in addition to air seeders.The frame of a modern agricultural implement can be 80 feet or morewide, and so the frame is divided into side by side wing sections thatpivot with respect to each other about frame pivot axes orientedparallel to the operating travel direction.

The front and rear frame wheels must support the weight of theimplements, and in addition, ground engaging tools are often configuredto draw them selves into the ground, thereby exerting additionaldownward forces that must be carried by the wheels. Compounding thisproblem is the fact that on floating hitch implements, the tractordrawbar is often lower than the hitch pivot axis, which results in anadditional downward force component on the front of the frame,especially on the center section where the hitch is attached. Thus insoft soil conditions, the wheels, and the front wheels in particular,sink into the soil such that rolling resistance and draft forcesincrease significantly. Especially with frame mounted opener air seedersand cultivators without independent ground engaging tools, the depth ofpenetration of the ground engaging tools increases, which undesirablyincreases seed depth placement in an air seeder, and also furtherincreases draft in all implements. When the soil is very soft as in wetweather, the implement can become stuck, and it is not then possible tocarry on the seeding operation.

Significant problems with wet conditions at seeding time wereencountered for example in large areas of western Canada during thespring of both 2010 and 2011, with many fields going unseeded becausethe window of suitable time closed before the fields were dry enough forthe farmers to operate their seeding equipment.

Considerable advice was circulated with respect to working wet fieldswith air seeders, such as reducing down pressure on furrow openers,changing packer wheels, altering travel paths, and the like. It wasgenerally accepted that air seeders with independent ground followingopeners worked better, but in many areas the soil was too wet for theseair seeders. Many farmers seeded by simply broadcasting seed on thesoil, often from airplanes.

Significant effort was devoted to providing increased flotation for airseeders in an attempt to keep them operative in very wet fieldconditions. Some offered larger front caster wheel tires in an attemptto provide increased flotation, however it is not possible tosignificantly increase the diameter of the tires. Some farmers fittedtrack assemblies in place of the front caster wheels. Seed Master™ ofRegina, Canada recommended an optional lift kit for their air seeders toreduce the problem of getting stuck. The lift kit reduced the weight onthe front caster wheels by transferring weight from the front casterwheels to the tractor drawbar and to the rear wheels through anarrangement described in Canadian Patent Application Number 2,645,522.

Increasing the diameter of a wheel generally provides a greaterimprovement in flotation and reduced rolling resistance compared toincreasing the wheel width, and so it is desirable to provide largerdiameter wheels. The diameter of the fixed rear wheels may be increasedsignificantly to provide an increased support area of contact with theground, however increasing the diameter of the castering front wheelsthat are pivotally attached to the frame through caster pivots isproblematic for a number of reasons.

The hitch to tow the implement is attached to the center section, andthe front wheels supporting the center section must be mounted on eitherside of the hitch. In order to use a large diameter castering flotationtire on the front of this center section the castering wheels would needto be moved away from the hitch such that there is sufficient distanceon each side to provide a clear pivot envelope for the large diameterwheel to pivot between the caster axis and the hitch as it pivotsthrough 360 degrees. In some implements it is known to support the frontof the center section with a single caster wheel assembly in the middleof the center section, instead of mounting one on each side, howeverwith larger implements with wing sections extending from each side ofthe center section, this arrangement lacks stability, especially when intransport.

If the size of the front caster wheel is increased significantly, suchas to twice the diameter for example, the caster bracket will need to besignificantly larger, stronger, and more costly. The distance betweenthe caster axis and the wheel/ground contact surface increasesproportionally, and the 360 degree envelope becomes problematic. Movingthese center section front caster wheels wide enough apart to providethis clear envelope results in an excessive distance between the wheels,such that travel on roads during transport is difficult, if notimpossible. The wider spacing also adversely affects ground contourfollowing characteristics of the implement.

Such agricultural implements typically make a sharp turn at the end of afield pass, and the caster wheels twist against the ground as the casteraxis moves sharply with the implement frame causing soil disturbance.The twisting of a larger tire against the ground surface will exertincreased forces on the caster bracket, and also create a larger soildisturbance. Such soil disturbance is particularly undesirable in modernno-till farming practices because conventional tillage is not carriedout on the field surface, and so any ruts and disturbance made by animplement are not smoothed out by normal cultivation.

Thus increasing the diameter of the front wheels of agriculturalimplements would be highly beneficial by providing increased flotation,however the diameter is constrained by the need to allow the frontcaster wheels to pivot to vary the rolling orientation thereof and allowthe front end of the implement to move laterally during turns.

BRIEF SUMMARY

It is an object of embodiments of the present disclosure to provide anagricultural implement apparatus with increased flotation that overcomesproblems in the prior art.

The increased flotation allows an air seeder as disclosed herein tooperate in soft soil conditions where prior art air seeders would sinkinto the soil and become stuck. The number of days in a farmer'sacceptable window of time for seeding where the seeder can be operatedin wet soil conditions is increased, thus providing significantfinancial benefits in wet years when seeding of the crop in the limitedwindow is not otherwise possible.

To allow the diameter of the front wheels to be increased, theorientation of the front wheels that were formerly allowed to caster iscontrolled so that the size of the clear envelope required for movementof the front wheels is reduced. The pivoting range of the front wheelscould be limited to something less than 360 degrees by providing stopsto restrict the rolling orientation of the castering wheels to a lesserangle, such as that required to turn a corner, however it would not thenbe possible to move the implement in reverse.

In a caster type wheel, the vertical caster axis is ahead of therotational axis of the wheel in the direction of travel, and ahead ofthe contact surface between the wheel and the ground that is directlyunder the rotational axis such that the caster axis and contact surfaceare substantially aligned in the direction of movement with the wheeltrailing behind the caster axis. The wheel pivots freely about thecaster axis and will pivot about the caster axis to assume thisrelationship.

During a turn, the caster bracket attached to the implement frame thatdefines the vertical caster axis moves laterally and the caster wheelassembly pivots about the vertical caster axis to maintain the alignmentin the new travel direction, and the rolling orientation of the wheelchanges to follow the implement frame. When the implement moves inreverse, as the caster bracket starts to move rearward, the wheel mayinitially roll rearward ahead of the caster axis, but as soon as theground contact surface and caster axis are no longer exactly aligned inthe travel direction, the caster wheel will pivot about 180 degrees inone direction or the other so the wheel is trailing behind the casteraxis. Because the wheel must pivot in either direction, an open pivotenvelope must be provided that allows the caster wheel to pivot through360 degrees.

In embodiments, the size of the clear envelope is reduced by controllingthe rolling orientation of the front wheels instead of allowing thewheels to pivot freely through 360 degrees as in the prior art. Thus thesize of the clear pivot envelope that must be provided to allow thefront wheels to pivot through the required operational range is muchreduced, and the large flotation front wheels can be located close tothe hitch.

In one embodiment, an agricultural implement apparatus comprising aframe supported on rear wheels and at least one front flotation wheelfor movement along the ground in an operating travel direction, and aplurality of ground engaging tools mounted on the frame substantiallyequally on each side of a frame axis extending parallel to the operatingtravel direction is provided. The at least one front flotation wheel ispivotally mounted to the frame about a substantially vertical wheelpivot axis. A hitch tongue has a rear end pivotally attached to alateral mid-point of the frame about a substantially vertical hitchpivot axis located substantially on the frame axis, and a front endadapted for pivotal attachment to a drawbar of a towing vehicle by asubstantially vertical drawbar pin. A wheel control mechanism connectsthe at least one front flotation wheel to the hitch tongue such thatpivotal movement of the at least one front flotation wheel about thewheel pivot axis follows pivotal movement of the hitch tongue about thehitch pivot axis. The wheel control mechanism is configured such thatwhen the hitch tongue is in a neutral position aligned with the frameaxis, the at least one front flotation wheel is oriented to roll in theoperating travel direction, and pivoting the hitch tongue about thehitch pivot axis away from the neutral position causes the at least onefront flotation wheel to pivot about the wheel pivot axis.

In a second embodiment, a method of controlling the rolling orientationof at least one front flotation wheel of an agricultural implement isprovided. The method comprises supporting a frame on rear wheels and theat least one front flotation wheel for movement along the ground in anoperating travel direction, and mounting a plurality of ground engagingtools on the frame substantially equally on each side of a frame axisextending parallel to the operating travel direction; pivotally mountingthe at least one front flotation wheel to the frame about asubstantially vertical wheel pivot axis; pivotally attaching a hitchtongue at a rear end thereof to a lateral mid-point of a width of theframe about a substantially vertical hitch pivot axis locatedsubstantially on the frame axis, and pivotally attaching a front end ofthe hitch tongue to a tow vehicle drawbar with a substantially verticaldrawbar pin; connecting the at least one front wheel to the hitch tonguewith a wheel control mechanism configured such that when the hitchtongue is in a neutral position the at least one front wheel is orientedto roll in the operating travel direction, and such that pivotalmovement of the at least one front wheel about the wheel pivot axisfollows pivotal movement of the hitch tongue about the hitch pivot axis;and operating the tow vehicle to tow the frame along a field surfacewith the ground engaging tools penetrating the field surface.

The devices and methods disclosed herein thus addresses the problem ofmounting large diameter flotation wheels on the front of the implementby providing a control mechanism for the rolling orientation of at leastthe center front wheels located on either side of the hitch. These largediameter wheels can thus be mounted about as close to the hitch as theprior art castering front wheels, such that road travel and contourfollowing characteristics are not adversely affected. In addition toallowing for larger tires, the control apparatus improves performance onturns in the field, reducing soil disturbance as compared to freelycastering wheels when in the field, and improves maneuverability when intransport. In another embodiment, a pivot restraint mechanism can alsobe operative to selectively secure the hitch tongue in the neutralposition to reduce skewing tendencies when in field operation.

Additionally, the large diameter of the tire allows the tire to rollover soil that is often loosened and piled up by the spinning action oftractor tires. The situation that is created by the spinning action ofthe tractor tires can cause smaller diameter tires to stop turning,begin skidding and begin piling up soil ahead of the tire, which greatlyincreases the force required to tow the drill. This in turn increasesthe spinning action of the tractor tires as they attempt to apply moreforce to overcome the increasing resistance, and eventually the seedingimplement can become stuck. The spinning action of the tractor tiresalso typically causes the tires on the air seeder that follow thetractor tires to drop relative to the nominal soil surface. When thedepth of the seeding opener is partially controlled by the front wheelon the drill frame, the seeding depth is also adversely affected and thedraft required to tow the seeding implement is increased therebyincreasing the spinning action of the tires which further drops thedepth of the seeding openers until the seeding unit become stuck. Attimes, the combination of the caster wheels skidding and piling up wetsoil and the seeding openers dropping causes the seeding implement andtractor to become stuck.

BRIEF DESCRIPTION OF THE DRAWING

While the invention is claimed in the concluding portions hereof,preferred embodiments are provided in the accompanying detaileddescription which may be best understood in conjunction with theaccompanying diagrams where like parts in each of the several diagramsare labeled with like numbers, and where:

FIG. 1 is a schematic top view of an embodiment of an agriculturalimplement apparatus where the front flotation wheels are casteringwheels and the wheel control mechanism is provided by control arms;

FIG. 2 is a schematic top view of an alternate embodiment of anagricultural implement apparatus as disclosed herein where the frontflotation wheels are mounted about a vertical wheel pivot axis locateddirectly above the rotational axes of the front flotation wheels, andwhere the wheel control mechanism is provided by control arms;

FIG. 3 is a schematic top view of an alternate embodiment of anagricultural implement apparatus where the front flotation wheels aremounted about a vertical wheel pivot axis located directly above therotational axes of the front flotation wheels, and where the wheelcontrol mechanism is provided by connected hydraulic cylinders;

FIG. 4 is a schematic top view of the embodiment of FIG. 3 with thehitch tongue in a leftward turning position, and the front flotationwheels turned to the left;

FIG. 5 is a schematic perspective view of an embodiment of anagricultural implement apparatus;

FIG. 6 is a top view of the embodiment of FIG. 5 with the hitch tonguein a leftward turning position;

FIG. 7 is a top view of the embodiment of FIG. 5 with the hitch tonguein the neutral position and with a pivot restraint mechanism installedand in the release position;

FIG. 8 is a top view of the embodiment of FIG. 7 with the hitch tonguein the neutral position and with the pivot restraint mechanism in therestraint position;

FIG. 9 is a top view of the embodiment of FIG. 7 with the hitch tonguein a leftward turning position and with the pivot restraint mechanism inthe release position;

FIG. 10 is a top view of the embodiment of FIG. 5 with the outboardcastering front wheels replaced by much larger outboard front wheelswith a controlled rolling orientation;

FIG. 11 is a top view of the embodiment of FIG. 10 with the hitch tonguein a leftward turning position, and the flotation front wheels andcontrolled flotation outboard front wheels oriented to roll to the left;

FIG. 12 is a top view of the embodiment of FIG. 10 with a pivotrestraint mechanism installed and in the release position and with thehitch tongue in the neutral position and the controlled flotation frontwheels and controlled flotation outboard front wheels oriented to rollin the operating travel direction;

FIG. 13 is a top view of the embodiment of FIG. 10 with the pivotrestraint mechanism in the restraint position with the hitch tongue inthe neutral position;

FIG. 14 is a top view of the embodiment of FIG. 10 with the pivotrestraint mechanism in the release position and with the hitch tongue ina leftward turning position and the controlled flotation front wheelsand controlled flotation outboard front wheels oriented to roll to theleft;

FIG. 15 schematically illustrates skewing of the implement frame aboutthe hitch pivot axis;

FIG. 16 schematically illustrates skewing of the implement frame aboutthe drawbar pivot axis;

FIG. 17 schematically illustrates a basic embodiment of a pivotrestraint mechanism that is provided by a lock pin movable from a lockedposition, engaging the hitch tongue and the frame in the neutralposition, to an unlocked position releasing the hitch tongue to pivotfreely.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates an embodiment of an agriculturalimplement apparatus 1. The apparatus 1 comprises a frame 3 supported formovement along the ground in an operating travel direction T on rearwheels 5, right and left outboard castering front wheels 7, and rightand left controlled flotation front wheels 9. A plurality of groundengaging tools 11, for example the furrow openers of an air seeder orcultivator shanks, are mounted on the frame 3 substantially equally oneach side of a frame axis FA extending parallel to the operating traveldirection. The rear wheels 5 are fixed to the frame such that rotationalaxes thereof are perpendicular to the operating travel direction T. Theright and left outboard castering front wheels 7 pivot freely aboutsubstantially vertical caster axes CA.

Front flotation wheels 9 are illustrated as the conventional casteringtype wheels pivotally mounted to the frame 3 on wheel arms 13 aboutsubstantially vertical wheel pivot axes provided by caster axes CA′located forward of the rotational axes RA of the flotation wheels 9,however the front flotation wheels 9 have a diameter that is about twicethe diameter of the rear wheels 5 and outboard castering front wheels 7and are much wider as well. The smaller wheels 5 and 7 are shown as dualwheel assemblies, with two side by side wheels instead of the singlelarge diameter front flotation wheel 9, however the larger single wheeldoes provide increased floatation compared to the smaller diameter dualwheels.

A hitch tongue 15 has a rear end pivotally attached to a lateralmid-point of the frame, located substantially on the frame axis FA,about a substantially vertical hitch pivot axis HPA, and has a front endadapted for pivotal attachment to the drawbar 17 of a tractor or liketowing vehicle by a substantially vertical drawbar pin 19 which providesa substantially vertical drawbar pivot axis DPA.

A wheel control mechanism 21 connects the front flotation wheels 9 tothe hitch tongue 15 such that pivotal movement of the front flotationwheels 9 about the caster axes CA′ follows pivotal movement of the hitchtongue 15 about the hitch pivot axis HPA. The wheel control mechanism 21is configured such that when the hitch tongue 15 is in a neutralposition NP aligned with the frame axis FA, the front flotation wheels 9are oriented to roll in the operating travel direction T, and pivotingthe hitch tongue 15 about the hitch pivot axis HPA away from the neutralposition NP causes the front flotation wheels 9 to pivot about thecaster axes CA′, as schematically illustrated in FIG. 1 where moving thehitch 15 to the left, as in making a left turn, turns the rollingorientation of the front flotation wheels 9 to the left to follow theleft turn.

In the embodiment of FIG. 1, the wheel control mechanism 21 is providedby right and left control arms 22 connect corresponding right and leftflotation front wheels 9 to the hitch tongue 15 at a control axis CTAforward of the hitch pivot axis HPA. The right and left control arms 22are configured such that pivoting the hitch tongue 15 about the hitchpivot axis HPA away from the neutral position NP causes the right andleft flotation front wheels 9 to pivot about the corresponding casteraxes CA′ such that front edges of the right and left flotation frontwheels 9 move in the same direction as the hitch tongue 15,substantially as illustrated in FIG. 2. When the hitch tongue 15 is inthe neutral position NP the right and left front flotation wheels 9 areoriented to roll in the operating travel direction T.

Thus the rolling orientation of the front flotation wheels 9 iscontrolled by the position of the hitch tongue 15. When the hitch tongue15 moves laterally during a turn, the front flotation wheels 9 turn inthe same direction.

It can be seen in FIG. 1 that when the castering front flotation wheels9 pivot about the caster axes CA′, the clear envelope required formovement of the front flotation wheels 9 about the caster axes CA′ mustbe large enough to accommodate the distance from the caster axis CA′ tothe rear edge of the wheel 9. The wheel 9 is offset rearward from thecaster axis CA′ and so the entire width of the wheel 9 must move towardthe forward extending hitch section 3H of the frame 3.

FIG. 2 therefore schematically shows a more advantageous embodiment ofan agricultural implement apparatus 1′ where the front flotation wheels9′ are pivotally mounted to the frame 3 about substantially verticalwheel pivot axes WPA located directly above the rotational axes RA ofthe flotation wheels 9′. Since pivotal movement of the front flotationwheels 9′ is controlled, the castering configuration is not required.The wheel control mechanism 21 is again provided by right and leftcontrol arms 22 substantially the same as in FIG. 1 that connectcorresponding right and left flotation front wheels 9′ to the hitchtongue 15 at the control axis CTA forward of the hitch pivot axis HPA.

Thus in the apparatus 1′ of FIG. 2, when the front flotation wheels 9′pivot about the wheel pivot axes WPA, the clear envelope required forpivotal movement of the front flotation wheels 9 is reduced compared tothe castering front flotation wheels 9 of FIG. 1. The wheel 9′ is notoffset rearward from the wheel pivot axis as in FIG. 1, and so only onehalf the width of the wheel 9′ moves toward the forward extending hitchsection 3H of the frame 3, and the wheel arms 13′ can be located closerto the forward extending hitch section 3H of the frame 3. It iscontemplated that it may be desirable to shorten the wheel arms 13′further and move the wheel pivot axis WPA behind the rotational axis RAof the front flotation wheels 9′.

FIGS. 3 and 4 schematically illustrate a further alternate agriculturalimplement apparatus 1″ where the front flotation wheels 9″ are mountedon wheel pivot axes WPA″ above the rotational axes RA″ of the wheels 9″,the same as in the apparatus 1′ shown in FIG. 2, but in the illustratedapparatus 1″, the wheel control mechanism 21″ is provided by hydrauliccylinders. A left pair of control hydraulic cylinders 24 comprises afirst hydraulic cylinder 24A connected to the hitch tongue 15″ and tothe frame 3, and a second hydraulic cylinder 24B connected to the frame3 and to the left front flotation wheel 9L″. Chambers of the first andsecond hydraulic cylinders 24A, 24B are connected or slaved such thatmovement of the hitch tongue 15″ away from the neutral position NP shownin FIG. 3 moves hydraulic fluid from the first hydraulic cylinder 24Ainto the second hydraulic cylinder 24B to pivot the left front flotationwheel 91″ about the wheel pivot axis WPA″ in the direction moved by thehitch tongue 15″.

In the apparatus 1″ illustrated in FIG. 3 the hitch tongue 15″ extendsrearward of the hitch pivot axis HPA and the first hydraulic cylinder24A of the left pair of control hydraulic cylinders 24 is connected tothe hitch tongue 15″ rearward of the hitch pivot axis HPA and on theside of the hitch tongue 15″ opposite the left front flotation wheels9L″. Thus when the hitch tongue 15″ moves to the left, the firsthydraulic cylinder 24A extends and hydraulic fluid is pushed into thesecond hydraulic cylinder 24B which retracts and turns the left frontflotation wheel 9L″ to the left, as illustrated in FIG. 4

In the same manner a right pair of control hydraulic cylinders 25comprises a first hydraulic cylinder 25A connected to the hitch tongue15″ rearward of the hitch pivot axis HPA and to the frame 3, and asecond hydraulic cylinder 25B connected to the frame 3 and to the rightfront flotation wheel 9R″. Chambers of the first and second hydrauliccylinders 25A, 25B are connected such that movement of the hitch tongue15″ away from the neutral position NP moves hydraulic fluid from thefirst hydraulic cylinder 25A into the second hydraulic cylinder 25B topivot the right front flotation wheel 9R″ in the direction moved by thehitch tongue 15.

FIGS. 5-9 schematically illustrate an alternate embodiment of anagricultural implement apparatus 101. The apparatus 101 comprises aframe 103 supported for movement along the ground in an operating traveldirection T on rear wheels 105, right and left outboard castering frontwheels 107, and right and left controlled flotation front wheels 109. Aplurality of ground engaging tools 111, for example the furrow openersof an air seeder or cultivator shanks, are mounted on the frame 103substantially equally on each side of a frame axis FA extending parallelto the operating travel direction. The rear wheels 105 are fixed to theframe such that rotational axes thereof are perpendicular to theoperating travel direction T. The right and left outboard casteringfront wheels 107 pivot freely about substantially vertical caster axesCA.

The frame 103 comprises a forward extending hitch section 103H and anaxle member 113 is mounted at a front end of the hitch section 103Hsubstantially perpendicular to the operating travel direction T and in acenter of a width of the frame 103. It is contemplated that in largeimplements, the axle member 113 will be fixed with respect to the frame,and essentially form part of the frame. The right and left flotationfront wheels 109 are pivotally mounted to the frame 103 by mounting sameon corresponding right and left ends of the axle member 113 aboutsubstantially vertical right and left wheel pivot axes WPA. The axlemember 113 is substantially aligned with rotational axes of the rightand left flotation front wheels 109 when the flotation front wheels 109are rolling in the operating travel direction T.

It can be seen that the flotation front wheels 109 have a much largerdiameter as well as width than the outboard castering front wheels 107and thus provide significantly improved flotation for the center frontportion of the frame 103. It is contemplated that the front flotationwheels will have a diameter of greater than about four feet,substantially larger than conventional castering front wheels which aretypically up to about 40 inches in diameter, and in this description theterm “flotation wheel” generally refers to a wheel much larger thanconventional implement wheels, and in particular to wheels with adiameter greater than about four feet.

A hitch tongue 115 has a rear end pivotally attached to a lateralmid-point of the frame about a substantially vertical hitch pivot axisHPA, and has a front end adapted for pivotal attachment to the drawbar117 of a tractor or like towing vehicle by a substantially verticaldrawbar pin 119 which provides a substantially vertical drawbar pivotaxis DPA.

The wheel control mechanism 123 is provided by right and left controlarms 122 connecting corresponding right and left flotation front wheels109 to the hitch tongue 115 at a control axis CTA forward of the hitchpivot axis HPA. The right and left control arms 22 are configured suchthat pivoting the hitch tongue 115 about the hitch pivot axis HPA awayfrom the neutral position NP shown in FIG. 7, aligned with the frameaxis FA, causes the right and left flotation front wheels 109 to pivotabout the corresponding right and left wheel pivot axes WPA such thatfront edges of the right and left flotation front wheels 109 move in thesame direction as the hitch tongue 115, substantially as illustrated inFIG. 6. When the hitch tongue 115 is in the neutral position NP theright and left front flotation wheels 109 are oriented to roll in theoperating travel direction T.

Thus the rolling orientation of the front flotation wheels 109 iscontrolled by the position of the hitch tongue 115. When the hitchtongue 115 moves laterally during a turn, the front flotation wheels 109follow and turn in the same direction.

To allow the hitch tongue 115 to float to follow the ground, the hitchtongue 115 will typically comprise a rear tongue section 115R pivotallyattached to the frame about the substantially vertical hitch pivot axisHPA and a front tongue section 115F pivotally attached to the reartongue 115R section about a substantially horizontal tongue section axisTA, as illustrated in FIG. 7. For clarity of illustration of theprinciples of operation of the disclosed embodiments these features arenot shown on the other drawings.

The frame 103 and hitch tongue 115 are configured such that when thehitch tongue 115 is in a neutral position NP with respect to the hitchpivot axis, as illustrated in FIGS. 7 and 8, the hitch tongue 115 is ina desired operating orientation with respect to the frame 103, alignedwith the frame axis as shown in FIG. 7.

Especially in minimum tillage agricultural operations that are populartoday, there is considerable plant residue left on field soil surfaceswhere agricultural implements are used. Soil and plant residue aredisturbed by the ground engaging tools, and must flow around the tool asit moves through the soil. To provide room for soil and residue to flowaround the ground engaging tools, the tools are mounted to the frame ina number of generally parallel rows that are spaced apart from the frontof the frame to the rear of the frame. The frame 103 of the illustratedapparatus 101 therefore comprises parallel members 103P spaced from thefront to the rear of the frame, and the ground engaging tools 111 arespaced along the parallel members 103P, with equal numbers on each sideof the frame axis FA. Thus the ground engaging tools 111 on each row areseparated by a distance equal to three times the row spacing, providingample room for soil and plant residue to flow between the tools 111 oneach row.

When the frame 103, and thus parallel members 103P, are orientedperpendicular to the operating travel direction T, the ground engagingtools 111 engage the ground at substantially equally spaced furrows111F. This then is the desired orientation of the frame 103, and whenthe hitch tongue 115 is in the neutral position, it extends forward fromthe hitch pivot axis HPA in the center of the width of the frame 103 atthe frame axis FA, parallel to the operating travel direction T andaligned with the frame axis FA, and perpendicular to the parallelmembers 103P of the frame.

During operation, due to soil conditions, slopes, and the like, one sideof the frame 103 is often subjected to drag forces that are greater orless than those on the other side so that one side drags back and theframe 103 pivots about the drawbar pin axis DPA and moves along thefield at some angle that is not perpendicular to the operating traveldirection T. This is commonly called a skewed orientation and isundesirable since as the frame 103 skews, the furrows in the soil movefrom an equal spacing to an unequal spacing.

Where considerable weight is carried on the implement frame, such as insome air seeders where agricultural products are carried on the frame,skewing is not such a significant problem, as the weight on the wheelsincreases the drag force required to cause the frame to skew. In othercommon air seeders where the agricultural products are carried on aseparate cart, skewing can be more problematic. In such air seeders, toreduce skewing a pivot restraint mechanism 126 can be provided that isselectively operative to secure the hitch tongue 115 in the neutralposition NP as illustrated in FIGS. 7-8.

The desired equally spaced furrows 111F are provided when the frame 103is perpendicular to the operating travel direction T. Unequal forces onthe right and left sides of the frame 103 result in a net force K, asshown in FIGS. 15 and 16, which will cause the frame 103 to skew, whereone side of the frame moves backward and the other side moves forward.In a conventional hitch assembly, the hitch tongue is fixedperpendicular to the frame and the frame thus pivots about the drawbarpivot axis at the front of the hitch tongue.

However in order to provide control of the rolling orientation of thefront wheels, the hitch tongue 115 of the present apparatus 101 must beable pivot at the hitch pivot axis HPA much closer to the frame. In thatcase when the frame 103 skews or pivots in response to unequal forces,the front end of the frame 103 will move through an arc AF with a centerat the hitch pivot axis HPA, and the rear end of the frame 103 will movethrough an arc AR with a center at the hitch pivot axis HPA, asschematically illustrated in FIG. 15. It can be seen that, for any givendegree of skew, ground engaging tools along the rear of the frame 103will move laterally much farther than those on the front end of theframe 103, and the furrow spacing will be impaired with only arelatively small degree of skewing. It is generally accepted thatmaximum crop yields are attained when plants are evenly spread acrossthe field, so the unequal spacing of furrow openers on air seederscaused by implement skewing is undesirable.

With the pivot restraint mechanism 126 securing the hitch tongue 115 inthe neutral position, the frame 103 will pivot about the verticaldrawbar pivot axis DPA at the front of the hitch tongue 115, asschematically illustrated in FIG. 16. Then when the frame 103 skews inresponse to unequal forces, the front end of the frame 103 will movethrough an arc AF′ with a center at the drawbar pivot axis DPA, and therear end of the frame 103 will move through an arc AR′ with a center atthe drawbar pivot axis DPA. Relative lateral movement of the groundengaging tools on the front and rear ends of the frame 103 is muchreduced, and impairment of the furrow spacing is reduced. Thus the pivotrestraint mechanism 126 can be operated to engage the hitch tongue 115and when the implement apparatus 101 is moving generally straight in theoperating travel direction T, and then to disengage the hitch tongue 115and allow same to pivot about the hitch pivot axis HPA when it isdesired to turn the front flotation wheels 109, such as during a sharperturn.

In a very basic embodiment, such as is schematically illustrated in FIG.17, a pivot restraint mechanism 126′ could be provided by a lock pin 127movable from a locked position LP, illustrated in phantom lines,engaging the hitch tongue 115′ and the frame 103′ through holes in eachand thus securing the hitch tongue 115′ in the neutral position, to anunlocked position ULP where the lock pin 127 is disengaged from theholes in the hitch tongue 115′ and the frame 103′, and a control 128selectively operative to activate pin actuators 129 to move the pin 127to one of the locked position LP and the unlocked position ULP.

More conveniently, the pivot restraint mechanism 126 illustrated inFIGS. 7-9 comprises right and left extendable actuators 131 connectedbetween the frame 103 and hitch tongue 115.

The right extendable actuator 131R is movable from a restraint positionillustrated in FIG. 8, resisting rightward pivotal movement of the hitchtongue 115 away from the neutral position NP, to a release positionillustrated in FIG. 7 where the hitch tongue 115 is free to moverightward away from the neutral position NP. Similarly the leftextendable actuator 131L is movable from a restraint positionillustrated in FIG. 8, resisting leftward pivotal movement of the hitchtongue 15 away from the neutral position NP, to a release positionillustrated in FIG. 7 where the hitch tongue 115 is free to moveleftward away from the neutral position 15.

The extendable actuators 131 are provided in the illustrated apparatus101 by right and left hydraulic cylinders 131R, 131L. The right and lefthydraulic cylinders 131R, 131L are configured to be fully extended whenin the restraint position of FIG. 8 with the hitch tongue 115 in theneutral position, and are operated as bias elements operative to exert abias force BF resisting movement of the hitch tongue 115 away from theneutral position NP. An active hydraulic source 133 is connected to theright and left hydraulic cylinders 131R, 131L through a hydrauliccontrol 135 as schematically illustrated in FIG. 8 only. The hydrauliccontrol 135 is operative to move the hydraulic cylinders between therestraint position of FIG. 8 and the release position of FIG. 7. Beingfully extended in the restraint position, the hydraulic cylinders 131 inthat position do not exert any force against the hitch tongue, butmovement away from the neutral position tends to cause one of thehydraulic cylinders to retract and the bias force BF is then exerted toresist retraction. It is also contemplated that hydraulic cylinderscould instead be configured to be fully retracted when in the restraintposition and exert the bias force when a force is exerted to extend thehydraulic cylinders.

When the hydraulic cylinders 131 are in the restraint position,pressurized hydraulic fluid at an active pressure from the activehydraulic source 133 is directed into the hydraulic cylinders 131 toexert the bias force BF, and the active hydraulic source 133 isoperative to allow pressurized hydraulic fluid to pass out of thehydraulic cylinders 131 when a hitch force HF exerted on the hitchtongue 115 in a direction away from the neutral position NP exceeds thebias force BF, such that the hitch tongue 115 moves away from theneutral position NP against the bias force BF.

By this arrangement, movement of the hitch tongue 115 and thus pivotingof the front flotation wheels 109 is possible when the towing vehiclemakes a turn that exerts a sufficiently large hitch force HF to overcomethe bias force BF. It is contemplated that the uneven forces that causeskewing will pivot the hitch tongue 115 about the drawbar pivot axis DPAand will not generally be sufficiently large to overcome the bias forceBF and move the hitch tongue 115 from the neutral position NP. Thus thedesired operation with the hitch tongue 115 in the neutral position NPwill be maintained until the greater hitch forces HF generated during aturn are encountered.

Ideally to maintain equal furrow spacing it is desirable to drive acrossa field in straight lines, making a 180 degree turn at each end. Fieldshapes however are not always amenable to travelling in a straight lineand some curves and turns of greater or lesser degree are a common partof farm implement operations. The pressure control 135 is also operativeto adjust the active pressure to adjust the bias force BF to allowmovement of the hitch tongue 115, and thus turning of the frontflotation wheels 109, at a selected hitch force. Thus the bias force BFcan be adjusted so that in a gentle turn, the hitch tongue is maintainedin the neutral position NP, while in a sharper turn the hitch tongue 115can move away from the neutral position NP and turn the implementapparatus 101.

In the pivot restraint mechanism 126 of the illustrated apparatus 101,each of the right and left hydraulic cylinders 131 is pivotallyconnected at a rear end thereof to the forward extending hitch section103H of the frame 103 and at a front end thereof to a first end 137A ofa link member 137. The opposite second end 37B of the link member 137 ispivotally connected to the hitch tongue 115. Moving the hydrauliccylinders 131 to the restraint position by directing pressurizedhydraulic fluid into the hydraulic cylinders 131 such that the hydrauliccylinders 131 extend moves the first ends 137A of the link members 137against the hitch tongue 115, as shown in FIG. 8, and shifts the hitchtongue 115 to the neutral position NP. When the hydraulic cylinders 131are fully extended, the first ends 137A of the link members 137 arepositioned closely adjacent each side of the hitch tongue 115, andsecure the hitch tongue 115 in the neutral position.

Moving the hydraulic cylinders to the release position moves the firstends 137A of the link members 137 away from the hitch tongue 115 asshown in FIG. 7. The hydraulic cylinders 131 are fully extended when inthe restraint position and also fully retracted when in the releaseposition of FIG. 7. The hydraulic cylinders 131 and link members 137 areconfigured such that when the hydraulic cylinders 131 are in the releaseposition and the hitch tongue pivots leftward to a selected maximumdegree from the neutral position NP, as illustrated in FIG. 9, the firstend 137A of the left link member 137L connected to the left hydrauliccylinder 131L bears against the hitch tongue 115 and prevents pivotalmovement of the hitch tongue 115 beyond the selected maximum degreeshown in FIG. 9. Rightward movement of the hitch tongue 115 is similarlylimited.

The hydraulic control 135 acts as a pivot control selectively operativeto move the pivot restraint mechanism 126 from a restraint mode, wherethe hitch tongue 115 is secured in the neutral position, to a releasemode where the hitch tongue 115 is free to pivot about the hitch pivotaxis HPA. A tool control 139 is selectively operative to raise and lowerthe ground engaging tools 111 with respect to the frame 103.Conveniently the hydraulic pivot control 135 is operatively connected tothe tool control 139 such that when the ground engaging tools 111 areraised, the hydraulic pivot control 135 moves the pivot restraintmechanism 126 to the release mode, and when the ground engaging tools111 are lowered, the hydraulic pivot control 135 moves the pivotrestraint mechanism 126 to the restraint mode. When making straightpasses back and forth across a field, the ground engaging tools 111 aretypically raised at the end of each pass to facilitate making the 180degree turn. With this arrangement, when the ground engaging tools areraised, the pivot restraint mechanism 126 automatically releases thehitch tongue to pivot and provide pivotal movement of the frontflotation wheels 109.

The implement apparatus 1 will typically include a transport control 141selectively operative to move the frame 103 to a transport position byraising the wings 103W to an upright position. It is contemplated thatin most applications, when travelling in the transport position thepivot restraint mechanism 126 will be in the release mode so that thetowing tractor can maintain steering control of a heavy implement. Thisis also desirable when making a sharp turn, such as from the road into afield approach.

FIGS. 10-14 schematically illustrate a version of the implementapparatus 101′ where the outboard castering front wheels 107 of FIGS.1-5 are replaced by right and left controlled outboard front wheels 143of the same larger size as the central front flotation wheels 109 whichprovide significantly improved flotation for the outer front portions ofthe frame 103. The pivot restraint mechanism 126 as described above isadded to the implement apparatus 101′ in FIGS. 12-14.

The controlled outboard front wheels 143 are mounted to the frame 103about substantially vertical wheel pivot axes WPA, and a control linkageconnects the right and left controlled outboard front wheels 143 to thehitch tongue 115 such that moving the hitch tongue 115 away from theneutral position NP in a selected direction turns the controlledoutboard front wheels 143 in the selected direction. In the illustratedapparatus 101′, the rotational axes RA of the front flotation wheels 109and the controlled outboard front wheels 143 are substantially alignedwhen the wheels 109, 143 are oriented to roll in the operating traveldirection T as shown in FIG. 10. Thus the central and outer portions ofthe front of the frame 103 are supported along the aligned rotationalaxes RA, and the separation distance between the outboard front wheels143 and the rear wheels 105 is increased somewhat to provide the largerdiameter flotation wheels 143.

To provide a smooth turn, the control linkage is configured such thatmoving the hitch tongue 115 to a selected maximum degree from theneutral position, as illustrated in FIG. 11, pivots the right and leftcontrolled front flotation wheels 109 and the right and left controlledoutboard front wheels 143 about their respective vertical wheel pivotaxes WPA such that rotational axes RA of the right and left frontflotation wheels 109 and the right and left controlled outboard frontwheels 143 intersect generally at a desired turning axis E. FIGS. 7 and9 show a similarly located turning axis E, where the outboard frontwheels are castering wheels 107 pivoting about vertical caster axes CA.

In the illustrated apparatus 101′, the control linkage for thecontrolled outboard front wheels 143 comprises a right pair of controlhydraulic cylinders 145 comprising a first hydraulic cylinder 145Aconnected to the hitch tongue 115 and to the frame 103 at the forwardextending hitch section 103H thereof, and a second hydraulic cylinder145B connected to the frame 103 and to the right controlled outboardfront wheel 143R. Chambers of the first and second hydraulic cylinders145A, 145B are connected or slaved such that movement of the hitchtongue 115 away from the neutral position NP of FIG. 10 toward theturned position of FIG. 11 moves hydraulic fluid from the firsthydraulic cylinder 145A into the second hydraulic cylinder 145B to pivotthe right controlled outboard front wheel 143R and pivot same in thedirection moved by the hitch tongue 15.

The hitch tongue 115 extends rearward of the hitch pivot axis HPA andthe first hydraulic cylinder 145A of the right pair of control hydrauliccylinders 145 is connected to the hitch tongue 115 rearward of the hitchpivot axis HPA and on the side of the hitch tongue 115 opposite theright controlled outboard front wheel 143R. Thus as can be seen infigures, when the hitch tongue moves to the left as in FIG. 11, thefirst hydraulic cylinder 145A retracts and hydraulic fluid is pushedinto the second hydraulic cylinder 145B which extends and turns theright controlled outboard front wheel 143R to the left.

In the same manner a left pair of control hydraulic cylinders 147comprises a first hydraulic cylinder 147A connected to the hitch tongue115 rearward of the hitch pivot axis HPA and to the frame 103, and asecond hydraulic cylinder 147B connected to the frame 103 and to theleft controlled outboard front wheel 143L, wherein chambers of the firstand second hydraulic cylinders 147A, 147B are connected such thatmovement of the hitch tongue 115 away from the neutral position NP moveshydraulic fluid from the first hydraulic cylinder 147A into the secondhydraulic cylinder 147B to turn the left controlled outboard front wheel143L in the direction moved by the hitch tongue 115.

The disclosed devices thus provide controlled pivoting and turning ofthe front wheels of an agricultural implement that allows for the use ofsubstantially larger diameter front wheels to increase flotation supportand reduce the tendency of the front end of such implements to sink intosoft soil, thus allowing the implement to operate on soft soil where thewheels of conventional implements would sink and the implement would bestuck and unable to work. Increased flotation also improves depthcontrol, decreases draft, and reduces ruts that adversely affectsubsequent field operations such as harvesting. Controlled pivoting ofthe front wheels also reduces stresses on the implement during turns.

The disclosed devices thus provide a method of controlling the rollingorientation of at least one front flotation wheels of an agriculturalimplement 1. The method comprises supporting a frame on front and rearwheels 5, 7, 9 for movement along the ground in an operating traveldirection T, and mounting a plurality of ground engaging tools 11 on theframe 3; pivotally mounting front flotation wheels 9 to the frame 3about vertical wheel pivot axes WP; pivotally attaching a hitch tongue15 to a mid-point of a width of the frame 3 about a substantiallyvertical hitch pivot axis HPA, and pivotally attaching a front end ofthe hitch tongue 15 to a to tow vehicle drawbar 17 with a substantiallyvertical drawbar pin 19; connecting the front flotation wheels 9 to thehitch tongue 15 with a wheel control mechanism comprising control arms22 or control hydraulic cylinders 24 configured such that when the hitchtongue 15 is in a neutral position NP the front flotation wheels 9 areoriented to roll in the operating travel direction T; operating the towvehicle to tow the frame 3 along a field surface with the groundengaging tools 11 penetrating the field surface.

The method can further comprise, as illustrated in FIGS. 7-9, operatingthe tow vehicle to tow the frame 103 along the field surface in asubstantially straight line with the hitch tongue 115 secured in theneutral position NP about the hitch pivot axis HPA, the neutral positionNP selected to place the hitch tongue 115 in a desired operatingorientation with respect to the frame 103; and releasing the hitchtongue 15 from the neutral position NP and turning the tow vehicle suchthat the hitch tongue 115 pivots about the hitch pivot axis HPA andmoves the wheel control mechanism 126 to pivot the front flotationwheels 109 about the wheel pivot axes WPA and turn the frame 103 in thesame direction as the tow vehicle.

The method can further comprise exerting a bias force BF on the hitchtongue 115 resisting movement of the hitch tongue 115 away from theneutral position NP, the bias force BF selected such that when operatingthe tow vehicle to tow the frame 103 in a substantially straight linealong a field surface with the ground engaging tools 111 penetrating thefield surface the hitch tongue 115 is secured in the neutral positionNP, and when the tow vehicle is turned the hitch tongue 115 pivots aboutthe hitch pivot axis HPA against the bias force BF. The bias force BF isexerted by a pivot restraint mechanism 126 when the pivot restraintmechanism 126 is in a restraint mode, and no bias force is exerted onthe hitch tongue 115 when the pivot restraint mechanism 126 is in arelease mode. The pivot restraint mechanism 126 is operated in therestraint mode when turns are in a first shallow range of turn degree,and the pivot restraint mechanism is operated in the release mode whenturns are in a second sharp range of turn degree.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous changes and modifications willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly, all such suitable changes or modificationsin structure or operation which may be resorted to are intended to fallwithin the scope of the claimed invention.

What is claimed is:
 1. An agricultural implement apparatus comprising: aframe supported on rear wheels and at least one front flotation wheelfor movement along the ground in an operating travel direction, and aplurality of ground engaging tools mounted on the frame substantiallyequally on each side of a frame axis extending parallel to the operatingtravel direction; wherein the at least one front flotation wheel ispivotally mounted to the frame about a substantially vertical wheelpivot axis; a hitch tongue having a rear end pivotally attached to alateral mid-point of the frame about a substantially vertical hitchpivot axis located substantially on the frame axis, and having a frontend adapted for pivotal attachment to a drawbar of a towing vehicle by asubstantially vertical drawbar pin; a wheel control mechanism connectingthe at least one front flotation wheel to the hitch tongue such thatpivotal movement of the at least one front flotation wheel about thewheel pivot axis follows pivotal movement of the hitch tongue about thehitch pivot axis. the wheel control mechanism configured such that whenthe hitch tongue is in a neutral position aligned with the frame axis,the at least one front flotation wheel is oriented to roll in theoperating travel direction, and pivoting the hitch tongue about thehitch pivot axis away from the neutral position causes the at least onefront flotation wheel to pivot about the wheel pivot axis.
 2. Theapparatus of claim 1 wherein the at least one front flotation wheel hasa diameter of greater than about four feet.
 3. The apparatus of claim 1wherein the frame and ground engaging tools are configured such thatwhen the frame is oriented perpendicular to the operating traveldirection, the ground engaging tools engage the ground at substantiallyequally spaced furrows, and when the hitch tongue is in the neutralposition, the hitch tongue is in the desired operating orientation withrespect to the frame and extends forward substantially parallel to theoperating travel direction and aligned with the frame axis.
 4. Theapparatus of claim 1 wherein the wheel control mechanism comprises acontrol arm connected between the hitch tongue and the at least onefront flotation wheel.
 5. The apparatus of claim 1 wherein the wheelcontrol mechanism comprises a first hydraulic cylinder connected betweenthe hitch tongue and the frame and a second hydraulic cylinder connectedbetween the at least one front flotation wheel and the frame, andwherein the first and second hydraulic cylinder are connected such thatsuch that pivotal movement of the hitch tongue about the hitch pivotaxis moves hydraulic fluid from the first hydraulic cylinder into thesecond hydraulic cylinder to pivot the at least one front flotationwheel about the wheel pivot axis.
 6. The apparatus of claim 1 whereinthe frame comprises a hitch section and comprising an axle membermounted at a front end of the hitch section substantially perpendicularto the operating travel direction and in a center of a width of theframe, and comprising right and left flotation front wheels mounted oncorresponding right and left ends of the axle member about correspondingright and left substantially vertical wheel pivot axes.
 7. The apparatusof claim 6 wherein the axle member is substantially aligned withrotational axes of the right and left flotation front wheels when theflotation front wheels are rolling in the operating travel direction. 8.The apparatus of claim 6 wherein the wheel control mechanism comprisesright and left control arms connecting corresponding right and leftflotation front wheels to the hitch tongue forward of the hitch pivotaxis, the right and left control arms configured such that when thehitch tongue is in the neutral position the right and left flotationfront wheels are oriented to roll in the operating travel direction, andsuch that pivoting the hitch tongue about the hitch pivot axis causesthe right and left flotation front wheels to pivot about thecorresponding right and left wheel pivot axes such that front edges ofthe right and left flotation front wheels move in the same direction asthe hitch tongue.
 9. The apparatus of claim 8 comprising right and leftflotation outboard front wheels mounted to the frame about substantiallyvertical wheel pivot axes, and a control linkage connecting the rightand left flotation outboard front wheels to the hitch tongue such thatmoving the hitch tongue away from the neutral position in a selecteddirection turns the flotation outboard front wheels in the selecteddirection.
 10. The apparatus of claim 9 wherein moving the hitch tongueto a selected maximum degree from the neutral position pivots the rightand left flotation front wheels and the right and left flotationoutboard front wheels about their respective vertical wheel pivot axessuch that rotational axes of the right and left flotation front wheelsand the right and left flotation outboard front wheels intersect at adesired turning axis.
 11. The apparatus of claim 10 wherein the desiredturning axis is located outside the frame.
 12. The apparatus of claim 9comprising a right pair of control hydraulic cylinders comprising afirst hydraulic cylinder connected to the hitch tongue and to the frame,and a second hydraulic cylinder connected to the frame and to the rightflotation outboard front wheel, wherein chambers of the first and secondhydraulic cylinders are connected such that movement of the hitch tongueaway from the neutral position moves hydraulic fluid from the firsthydraulic cylinder into the second hydraulic cylinder to turn the rightflotation outboard front wheel in the direction moved by the hitchtongue.
 13. The apparatus of claim 12 wherein the hitch tongue extendsrearward of the hitch pivot axis and the first hydraulic cylinder of theright pair of control hydraulic cylinders is connected to the hitchtongue rearward of the hitch pivot axis.
 14. The apparatus of claim 12comprising a left pair of control hydraulic cylinders comprising a firsthydraulic cylinder connected to the hitch tongue and to the frame, and asecond hydraulic cylinder connected to the frame and to the leftflotation outboard front wheel, wherein chambers of the first and secondhydraulic cylinders are connected such that movement of the hitch tongueaway from the neutral position moves hydraulic fluid from the firsthydraulic cylinder into the second hydraulic cylinder to turn the leftflotation outboard front wheel in the direction moved by the hitchtongue, and wherein the first hydraulic cylinder of the left pair ofcontrol hydraulic cylinders is connected to the hitch tongue rearward ofthe hitch pivot axis.
 15. The apparatus of claim 1 comprising a pivotrestraint mechanism selectively operative to secure the hitch tongue inthe neutral position.
 16. The apparatus of claim 15 wherein the pivotrestraint mechanism comprises at least one lock pin movable from alocked position, engaging the hitch tongue and the frame and securingthe hitch tongue in the neutral position, to an unlocked position wherethe at least one lock pin is disengaged from the hitch tongue and theframe, and a control selectively operative to move the lock pin to oneof the locked position and the unlocked position.
 17. The apparatus ofclaim 15 wherein the pivot restraint mechanism comprises an extendableactuator connected between the frame and hitch tongue.
 18. The apparatusof claim 17 comprising: a right extendable actuator movable from arestraint position, resisting rightward pivotal movement of the hitchtongue away from the neutral position, to a release position where thehitch tongue is free to move rightward away from the neutral position;and a left extendable actuator movable from a restraint position,resisting leftward pivotal movement of the hitch tongue away from theneutral position, to a release position where the hitch tongue is freeto move leftward away from the neutral position.
 19. The apparatus ofclaim 18 wherein the right and left extendable actuators are provided bycorresponding right and left extendable bias elements, the extendablebias elements configured to be one of fully extended and fully retractedwhen in the restraint position with the hitch tongue in the neutralposition, the extendable bias elements operative to exert a bias forceresisting movement of the hitch tongue away from the neutral position.20. The apparatus of claim 17 wherein: at least one extendable actuatoris pivotally connected at a first end thereof to a first end of a linkmember; wherein a second end of the link member is pivotally connectedto one of the hitch tongue and the frame; a second end of the at leastone extendable actuator is pivotally connected to the other of the hitchtongue and the frame; wherein moving the at least one extendableactuator to the restraint position moves the first end of the linkmember against the one of the hitch tongue and the frame to which thesecond end of the link member is connected, and wherein moving the atleast one extendable actuator to the release position moves the firstend of the link member away from the one of the hitch tongue and theframe to which the second end of the link member is connected.
 21. Theapparatus of claim 19 wherein the right and left extendible biaselements are provided by corresponding right and left hydrauliccylinders, and comprising an active hydraulic source connected to theright and left hydraulic cylinders through a hydraulic control, thehydraulic control operative to move the hydraulic cylinders to therestraint position, and operative to move the hydraulic cylinders to therelease position.
 22. The apparatus of claim 21 wherein, when thehydraulic cylinders are in the restraint position, pressurized hydraulicfluid at an active pressure from the active hydraulic source is directedinto the hydraulic cylinders to exert the bias force, and the activehydraulic source is operative to allow pressurized hydraulic fluid topass out of the hydraulic cylinders when a hitch force exerted on thehitch tongue in a direction away from the neutral position exceeds thebias force, such that the hitch tongue moves away from the neutralposition against the bias force.
 23. The apparatus of claim 22comprising a pressure control operative to adjust the active pressure toadjust the bias force.
 24. The apparatus of claim 22 wherein: each ofthe right and left hydraulic cylinders is pivotally connected at a firstend thereof to a first end of a corresponding link member; a second endof the link member is pivotally connected to one of the hitch tongue andthe frame; a second end of each hydraulic cylinder is pivotallyconnected to the other of the hitch tongue and the frame; wherein movingthe hydraulic cylinders to the restraint position by directingpressurized hydraulic fluid into the hydraulic cylinders moves the firstends of the link members against the one of the hitch tongue and theframe to which the second ends of the link members are connected; andwherein moving the hydraulic cylinders to the release position moves thefirst ends of the link members away from the one of the hitch tongue andthe frame to which the second ends of the link members are connected.25. The apparatus of claim 24 wherein the hydraulic cylinders are fullyextended when in the restraint position and fully retracted when in therelease position, and configured such that when the hydraulic cylindersare in the release position and the hitch tongue pivots leftward to aselected maximum degree from the neutral position, the first end of aleft link member connected to the left hydraulic cylinder bears againstthe one of the hitch tongue and the frame to which the second end of theright link member is connected, and prevents movement of the hitchtongue beyond the selected maximum degree.
 26. The apparatus of claim 17comprising a pivot control selectively operative to move the pivotrestraint mechanism from a restraint mode, where the hitch tongue issecured in the neutral position, to a release mode where the hitchtongue is free to pivot about the hitch pivot axis.
 27. The apparatus ofclaim 26 comprising a tool control selectively operative to raise andlower the ground engaging tools with respect to the frame, and whereinthe pivot control is operatively connected to the tool control such thatwhen the ground engaging tools are raised, the pivot control moves thepivot restraint mechanism to the release mode, and when the groundengaging tools are lowered, the pivot control moves the pivot restraintmechanism to the restraint mode.
 28. The apparatus of claim 1 whereinthe hitch tongue comprises a rear tongue section pivotally attached tothe frame about the substantially vertical hitch pivot axis and a fronttongue section pivotally attached to the rear tongue section about asubstantially horizontal tongue section axis.
 29. A method ofcontrolling the rolling orientation of at least one front flotationwheel of an agricultural implement, the method comprising: supporting aframe on rear wheels and on the at least one front flotation wheel formovement along the ground in an operating travel direction, and mountinga plurality of ground engaging tools on the frame substantially equallyon each side of a frame axis extending parallel to the operating traveldirection; pivotally mounting the at least one front flotation wheel tothe frame about a substantially vertical wheel pivot axis; pivotallyattaching a hitch tongue at a rear end thereof to a lateral mid-point ofa width of the frame about a substantially vertical hitch pivot axislocated substantially on the frame axis, and pivotally attaching a frontend of the hitch tongue to a tow vehicle drawbar with a substantiallyvertical drawbar pin; connecting the at least one front wheel to thehitch tongue with a wheel control mechanism configured such that whenthe hitch tongue is in a neutral position the at least one front wheelis oriented to roll in the operating travel direction, and such thatpivotal movement of the at least one front wheel about the wheel pivotaxis follows pivotal movement of the hitch tongue about the hitch pivotaxis; operating the tow vehicle to tow the frame along a field surfacewith the ground engaging tools penetrating the field surface.
 30. Themethod of claim 29 operating the tow vehicle to tow the frame along thefield surface in a substantially straight line with the hitch tonguesecured in the neutral position about the hitch pivot axis, the neutralposition selected to place the hitch tongue in a desired operatingorientation with respect to the frame; and releasing the hitch tonguefrom the neutral position and turning the tow vehicle such that thehitch tongue pivots about the hitch pivot axis and moves the wheelcontrol mechanism to pivot the at least one front wheel about the wheelpivot axis and turn the frame in the same direction as the tow vehicle.31. The method of claim 30 comprising exerting a bias force on the hitchtongue resisting movement of the hitch tongue away from the neutralposition, the bias force selected such that when operating the towvehicle to tow the frame in a substantially straight line along a fieldsurface with the ground engaging tools penetrating the field surface thehitch tongue is secured in the neutral position, and when the towvehicle is turned the hitch tongue pivots about the hitch pivot axisagainst the bias force.
 32. The method of claim 31 wherein the biasforce is exerted by a pivot restraint mechanism when the pivot restraintmechanism is in a restraint mode, and wherein no bias force is exertedon the hitch tongue when the pivot restraint mechanism is in a releasemode, and comprising operating the pivot restraint mechanism in therestraint mode when turns are in a first shallow range of turn degree,and operating the pivot restraint mechanism in the release mode whenturns are in a second sharp range of turn degree.